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Articles 2731 - 2760 of 3234

Full-Text Articles in Mechanical Engineering

Uncertainty Characterization Of Orbital Debris, Jolanta Matusewicz Aug 2006

Uncertainty Characterization Of Orbital Debris, Jolanta Matusewicz

Mechanical and Aerospace Engineering Theses - Archive

The increase of orbital debris in the low Earth orbit is a concern for the space industry. Spacecraft and satellites are at risk of collision with orbital debris. Collisions can damage sensitive components or result in catastrophic failure. Organizations such as the United States Space Command are responsible for tracking orbital debris using ground based sensor sites located around the world. Orbit determination techniques are used to estimate the position and velocity of the orbit using range, azimuth, and elevation measurements obtained from the sensors. Nine sensors from the Space Surveillance Network are simulated to track a debris object in …

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Analysis And Design Of A Piezoelectric Micro-Actuator, Po-Shiun Chen Aug 2006

Analysis And Design Of A Piezoelectric Micro-Actuator, Po-Shiun Chen

Mechanical and Aerospace Engineering Theses - Archive

Micro-grippers are usually fabricated of silicon using traditional semiconductor manufacturing processes and actuated based on thermal energy input causing their temperature to substantially increase and render unsuitable for certain applications such as biological tissue handling. In this research work, the design of a micro-gripper using piezoelectric ceramics (PZT) is presented as an alternative to silicon based micro gripper. The design procedure utilized ANSYS, a Finite Element Method based software tool to verify simple PZT models and subsequently evaluate the stroke for a family of configurations. The configurations were further explored and optimized considering that the fabrication would be performed using …

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Mems Packaging: Fluxless Soldering And Reliability Assessment, Amit L. Patil Aug 2006

Mems Packaging: Fluxless Soldering And Reliability Assessment, Amit L. Patil

Mechanical and Aerospace Engineering Theses - Archive

This thesis presents process development and reliability assessment of the fluxless packaging of the MEMS devices. This packaging consists of metallized Kovar package with side wall of same material and circular holes for the optical fiber interconnect between the microstructures on the chip and the macro-environment. The back of the MEMS chip and the soldering part of the optical fiber is metallized. A thin solder perform is placed between the chip and the metallized package to attach the chip and a circular solder perform is used to attach the fiber to the metal substrate. The soldering process is fluxless hence …

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Spacecraft Formation Flight: Analysis Of The Perturbed J2-Modified Hill-Clohessy-Wiltshire Equations, Jeffery Scott Ginn Aug 2006

Spacecraft Formation Flight: Analysis Of The Perturbed J2-Modified Hill-Clohessy-Wiltshire Equations, Jeffery Scott Ginn

Mechanical and Aerospace Engineering Theses - Archive

With the recent technological gains made in satellite design and manufacturing, there has been great interest in utilizing a cluster of satellites to perform the same tasks performed by larger satellites. Historically, this has been done utilizing the Clohessy-Wiltshire equations, or the Hill's equations, as a benchmark for understanding the physics of the relative motion between two spacecraft. A variety of different models have been derived and implemented to study the relative motion dynamics since the Hill-Clohessy-Wiltshire (HCW) equations. Some of these models, like the HCW equations, are linearized and have analytical solutions. These models make the underlying physics due …

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Effect Of Crac Location On A Fixed Rack Layout Of A Data Center, Vishwas Bedekar Aug 2006

Effect Of Crac Location On A Fixed Rack Layout Of A Data Center, Vishwas Bedekar

Mechanical and Aerospace Engineering Theses - Archive

Microprocessor driven escalation of thermal management needs has resulted in significant cooling challenges at the data center facility level, which can house thousands and tens of thousands of heat producing processors. Raised floor air ducting is the most common configuration, where chilled air from the air conditioning units is forced into the room via a under floor plenum and through perforated tiles on the floor. The hot air from the racks finds its way to the top of the air conditioning units and is then cooled and blown into the under floor plenum. The temperature at inlet of the racks …

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Analysis And Optimal Design Of Beams Using Radial Basis Function, Yung-Kang Sun Aug 2006

Analysis And Optimal Design Of Beams Using Radial Basis Function, Yung-Kang Sun

Mechanical and Aerospace Engineering Dissertations - Archive

The application of Multiquadric Radial Basis Function (MQ RBF) in the analysis and optimal design of beams are addressed in this dissertation. For static analysis, a new Least Square Collocation (LSC) method is introduced. For buckling and vibration analysis, Rayleigh-Ritz analysis procedures are presented using MQ RBF basis function. Numerical results show that LSC can provide better results than the classical collocation method when the same number of collocation points are used. In vibration analysis, MQ RBF-based Rayleigh-Ritz can be used to calculate natural frequency accurately for several hundred modes. The important question of choosing shift parameters is discussed and …

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Enhancement Of Cryoinjury By Use Of Eutectic Crystallization Of An Amino Acid Adjuvant, Chuo-Li Wang Aug 2006

Enhancement Of Cryoinjury By Use Of Eutectic Crystallization Of An Amino Acid Adjuvant, Chuo-Li Wang

Mechanical and Aerospace Engineering Theses - Archive

Enhancement of cryoinjury by use of eutectic formation was investigated to improve the efficacy of cryosurgery. Although the enhancement of cryoinjury associated with eutectic crystallization of sodium chloride (NaCl) has been demonstrated, its advantage can be maximized with adjuvants which are biocompatible and have higher eutectic temperature than NaCl. In this study, the feasibility of glycine, which is less toxic and have higher eutectic temperature than NaCl, was tested. Two groups of MCF-7 human breast cancer cell were suspended in isotonic saline with glycine, then were frozen and thawed on a directional solidification stage in the same protocol except that …

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Selection Of Attractor Sounds For An Audio-Based Navigation System For The Visually Impaired, Brad Salisbury Aug 2006

Selection Of Attractor Sounds For An Audio-Based Navigation System For The Visually Impaired, Brad Salisbury

Masters Theses

Research in to human hearing has been very ‘laboratory’ oriented in the sense that the test environments do not replicate most ‘real world’ situations [J.C. Middlebrooks and D.M. Green, Ann. Rev. of Psychology, 42, 135-159 (1991)]. While very useful information is gained from these types of tests, it is difficult to see how ‘real world’ situations affect sound source localization, recognition, and navigation (walking/way finding) performance. Such information is especially important to people who are visually impaired and dependent on prior knowledge of the environment or audio cues for travel. The research reported here was conducted during the development of …

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Parameters Affecting Critical Heat Flux Of Nanofluids: Heater Size, Pressure Orientation And Anti-Freeze Addition, Madhav Rao Kashinath Aug 2006

Parameters Affecting Critical Heat Flux Of Nanofluids: Heater Size, Pressure Orientation And Anti-Freeze Addition, Madhav Rao Kashinath

Mechanical and Aerospace Engineering Theses - Archive

This research aims at investigating the effect, heater size, pressure, heater orientation and effect of anti-freeze addition on critical heat flux of nanofluids which have shown large potentials as coolants for high power generating uses. Nanofluids have shown about ~180 - 200% enhancement in the critical heat flux values. The effect of heater size employing three different sized heaters yielded about ~180% enhancement over pure water. The effect of pressure on critical heat flux investigated by testing nanofluids at three pressures showed ~240% increase in critical heat flux. Surface orientation effect on critical heat flux carried out for a 2 …

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Development Of Three Block Thermal Compact Model And Verification Of Modified Linear Superposition Technique For Stacked Die, Suresh G. Nikalaje Aug 2006

Development Of Three Block Thermal Compact Model And Verification Of Modified Linear Superposition Technique For Stacked Die, Suresh G. Nikalaje

Mechanical and Aerospace Engineering Theses - Archive

Over the last few years an impressive amount of progress has been achieved in the field of compact modeling of chip packages. But available compact modeling methods could not address the issue of limitation on the mesh statistics which is major concern while modeling in FEM softwares with limited number of nodes and elements. It is not possible to attain convergence of solution for thermal simulation of detailed model with the constraint on the number of nodes and elements. In this thesis, a simple and straight forward three block (3B) compact modeling method is developed. 3B compact modeling method has …

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Crashworthiness Design Optimization Using Surrogate Models, Cheng-Ho Tho Jul 2006

Crashworthiness Design Optimization Using Surrogate Models, Cheng-Ho Tho

Mechanical and Aerospace Engineering Dissertations - Archive

Despite the advances in computer technology, the enormous computational cost associated with the large-scale and complex nonlinear crashworthiness simulations renders it to be impractical to rely exclusively on computer simulations for crashworthiness design optimization. A preferable strategy is to employ the computational efficient surrogate model in lieu of the expensive simulations to facilitate the optimization process and design concept exploration. An added advantage of the surrogate models is that they tends to eliminate the high-frequency numerical noise which may hinder the performance of the direct gradient-based optimization technique by constructing smooth crash responses in the crashworthiness analysis. Even thought the …

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Incorporating Solid Mechanics Into Biomedical And Life Sciences, Kai-Tak Wan Jul 2006

Incorporating Solid Mechanics Into Biomedical And Life Sciences, Kai-Tak Wan

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Integrating and interfacing solid mechanics and life sciences is challenging, but, with effort, the two disciplines can complement one another. This paper describes work ongoing at the Mechanical and Aerospace Engineering Department of the University of Missouri at Rolla on cellular biomechanics and mechanical characterization of single cells. Also discussed is the study of tissue biomechanics in understanding the mechanical aspects of lens accommodation in human vision.

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Attribute-Level Neighbor Hierarchy Construction Using Evolved Pattern-Based Knowledge Induction, Thanit Puthpongsiriporn, J. David Porter, Bopaya Bidanda, Ming En Wang, Richard E. Billo Jul 2006

Attribute-Level Neighbor Hierarchy Construction Using Evolved Pattern-Based Knowledge Induction, Thanit Puthpongsiriporn, J. David Porter, Bopaya Bidanda, Ming En Wang, Richard E. Billo

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Neighbor knowledge construction is the foundation for the development of cooperative query answering systems capable of searching for close match or approximate answers when exact match answers are not available. This paper presents a technique for developing neighbor hierarchies at the attribute level. The proposed technique is called the evolved Pattern-based Knowledge Induction (ePKI) technique and allows construction of neighbor hierarchies for nonunique attributes based upon confidences, popularities, and clustering correlations of inferential relationships among attribute values. The technique is applicable for both categorical and numerical (discrete and continuous) attribute values. Attribute value neighbor hierarchies generated by the ePKI technique …

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Most Probable Point-Based Design Optimization, Akhil R. Tipnis Jul 2006

Most Probable Point-Based Design Optimization, Akhil R. Tipnis

Mechanical & Aerospace Engineering Theses & Dissertations

Modem products ranging from simple components to complex systems should be designed to be optimal and reliable. The challenge of modem engineering is to ensure that manufacturing costs are reduced and design cycle times are minimized while achieving requirements for performance and reliability. If the market for the product is competitive, improved quality and reliability can generate very strong competitive advantages. Reliability based design optimization plays a very important role in designing almost any kind of product. This investigation focuses on the development of the hybrid PMNRIA approach which uses the active-in-reliability concept for reliability based design optimization. The efficiency …

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Unsteady Numerical Analysis Of A 2-Dimensional, Hydrogen Fueled, Air-Breathing Dual Mode Scramjet Engine, Nathan John Luetke Jul 2006

Unsteady Numerical Analysis Of A 2-Dimensional, Hydrogen Fueled, Air-Breathing Dual Mode Scramjet Engine, Nathan John Luetke

Mechanical & Aerospace Engineering Theses & Dissertations

Upstream interaction in a transient two-dimensional dual-mode scramjet engine is examined. This research is performed to compare completed and verified steady results with unsteady results in order to have a better understanding of the flow field. The flow is solved numerically with a Mach 2.5 free stream and sonic normal injection of hydrogen fuel emanating from facing walls while no symmetry assumptions were made. The free stream is modeled as vitiated air in order to produce comparable flight enthalpies and stagnation properties at the combustor inlet during flight conditions of approximately Mach 7. The vitiated stream consists of water vapor …

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Micron-Level Actuator For Thermal-Fluid Control In Microchannels, Nurhak Erbas Jul 2006

Micron-Level Actuator For Thermal-Fluid Control In Microchannels, Nurhak Erbas

Mechanical & Aerospace Engineering Theses & Dissertations

Effectiveness of an actuator is investigated for thermal-flow control in microchannels. First, simulations of a single actuator in a quiescent external medium are performed in order to study the parameters characterizing the synthetic jet flow from the actuator. For this purpose, a simplified, two-dimensional configuration is considered. The membrane motion is modeled in a realistic manner as a moving boundary in order to accurately compute the flow inside the actuator cavity. The geometric and actuation parameters of the actuator are investigated to define the effectiveness of the jet flow. The study is done initially at macro scales. Then, the flow …

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Air Jet Impingement For Levitation, James Frederick Huber May 2006

Air Jet Impingement For Levitation, James Frederick Huber

Mechanical and Aerospace Engineering Theses - Archive

Traditional part acquisition methods such as vacuum cups and robotic grippers do not meet the handling needs of truly fragile materials, because both of these methods require surface contact. An alternative to these traditional approaches is the use of air jet impingement for levitation. This technique confines impinged air to a thin disk above the target to form radial diffuser. The Bernoulli Effect causes a pressure difference between the fast-moving impinged air above the surface and ambient air below it. The net pressure difference is sufficient to lift objects weighing more than one kilogram using standard shop air. This method …

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Frequency Response Approximation Methods Of The Dissipative Model Of Fluid Transmission Lines, John King May 2006

Frequency Response Approximation Methods Of The Dissipative Model Of Fluid Transmission Lines, John King

Mechanical and Aerospace Engineering Theses - Archive

This thesis introduces an accurate and efficient method of obtaining a linear approximation for a nonlinear model of a complete fluid transmission line system using Matlab® Signal Processing Toolbox and Symbolic Math Toolbox programs. This technique is then packaged in a Graphical User Interface program to streamline the process of analyzing a total system. The method of approximating the frequency response of a fluid transmission line with a rational polynomial transfer function using the Matlab® 'invfreqs' least squares curve fitting algorithm has already been introduced. This research improves the technique by applying the 'invfreqs' command to a total system rather …

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Structural Optimization Using Femlab And Smooth Support Vector Regression, Divija Odapally May 2006

Structural Optimization Using Femlab And Smooth Support Vector Regression, Divija Odapally

Mechanical and Aerospace Engineering Theses - Archive

In recent years support vector machine (SVM) has been emerging as a popular tool for function approximation. Application of SVM for approximation of mathematical functions and complex engineering analysis has been represented by Palancz et al and Clarke et al, respectively. However the training of the original SVM involves the solution of a quadratic programming (QP) problem. This makes the application of SVM to large problem computationally expensive. To circumvent this difficulty, Lee et al developed a more efficient SVM formulation namely epsilon-SSVR which drastically improved the training efficiency of SVM. In this research the SSVR is used to build …

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Finite Element Analysis Of Moisture And Thermal Induced Stress In Flip Chip Packages, Santanu Ghosh May 2006

Finite Element Analysis Of Moisture And Thermal Induced Stress In Flip Chip Packages, Santanu Ghosh

Mechanical and Aerospace Engineering Theses - Archive

The process of moisture absorption and subsequent hygroswelling stress development is a cause of concern in the IC packaging industry. Also thermal stresses developed during the lead free reflow process with a high peak temperature (~ 250oC) add to the problem. In Flip Chip packages, the related effects are high shear stresses at the multilayer interfaces and normal stresses in solder balls. This can lead to phenomenon like delamination at the interfaces and UBM opening. In this work we have made an attempt to simulate the moisture absorption process, subsequent hygroswelling stress development, and thermal stress generated during reflow using …

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2nd Annual Undergraduate Research Conference Abstract Book, University Of Missouri--Rolla Apr 2006

2nd Annual Undergraduate Research Conference Abstract Book, University Of Missouri--Rolla

Undergraduate Research Conference at Missouri S&T

No abstract provided.

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Viscoplastic Finite-Element Simulation To Predict The Solder Joint Fatigue Life Of Different Flash Memory Die Stacking Architectures, Yong Je Lee Apr 2006

Viscoplastic Finite-Element Simulation To Predict The Solder Joint Fatigue Life Of Different Flash Memory Die Stacking Architectures, Yong Je Lee

Mechanical and Aerospace Engineering Theses - Archive

This thesis focuses on the viscoplastic finite-element simulation to predict the solder joint fatigue life of different die stacking architectures for flash memory products. Four different stacked package architectures were evaluated as follows: pyramid, rotated, and spacer stacking, while interconnection (solder joint) was held constant. Number of dies for all four stacking configurations were varied from three, five and seven. To keep the package height constant, the die and die attach thickness were varied and the resulting effects on the stresses were investigated. A quarter and half symmetry model of stacked flash package are generated using ANSYS APDL script. The …

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Numerical Study On Capillarity- Dominant Free Surface And Interfacial Flows, Zhaoyuan Wang Apr 2006

Numerical Study On Capillarity- Dominant Free Surface And Interfacial Flows, Zhaoyuan Wang

Mechanical and Aerospace Engineering Dissertations - Archive

The continuum surface force (CSF) method has been extensively employed in the volume-of-fluid (VOF), level set (LS) and front tracking methods to model surface tension forces. Its ability is limited for the surface tension dominant free surface and interfacial flows due to the existence of spurious currents. These currents may lead to disastrous interface instabilities and failure of grid convergence, which are present in all the previous versions of the CSF algorithm. In this study, a coupled level set and volume-of-fluid method (CLSVOF) is employed for interface tracking, which offers more accurate computations of the curvature and the normal vector …

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Boundary Interference Assessment And Correction For Open Jet Wind Tunnels Using Panel Methods, Wael Ahmed Mokhtar Apr 2006

Boundary Interference Assessment And Correction For Open Jet Wind Tunnels Using Panel Methods, Wael Ahmed Mokhtar

Mechanical & Aerospace Engineering Theses & Dissertations

The presence of nearby boundaries in a wind tunnel can lead to aerodynamic measurements on a model in the wind tunnel that differ from those that would be made when the boundaries of the moving fluid were infinitely far away. The differences, referred to as boundary interference or wall interference, can be quite large, such as when testing aircraft models developing high lift forces, or whose wingspan is a large fraction of the wind tunnel width, or high drag models whose frontal area is a large fraction of the tunnel cross section. Correction techniques for closed test section (solid walled) …

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Inertia Measurement And Dynamic Stability Analysis Of A Radio-Controlled Joined-Wing Aircraft, William A. Mcclelland Mar 2006

Inertia Measurement And Dynamic Stability Analysis Of A Radio-Controlled Joined-Wing Aircraft, William A. Mcclelland

Theses and Dissertations

Dynamic stability and stall during steady level turns were examined for VA-1, a joined-wing flight demonstrator aircraft. Configurations with a lower vertical tail and fairings over the main landing gear were compared with a recommendation on the combination had the best drag and dynamic stability characteristics. The dynamic stability analysis was broken into four key parts: a twist test experimentally measured mass moments of inertia, a panel method was used to find non-dimensional stability derivatives, lateral and longitudinal state space models estimated dynamic stability characteristics and handling quality levels were evaluated using a Cooper-Harper based rating system. VA-1 was found …

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Design, Build And Validation Of A Small-Scale Combustion Chamber Testing Facility, Eric R. Dittman Mar 2006

Design, Build And Validation Of A Small-Scale Combustion Chamber Testing Facility, Eric R. Dittman

Theses and Dissertations

This study investigated the design parameters necessary for the construction and use of a testing facility built to test the combustor section of engines. User inputs were acquired by interview and used in the decisions made in arrangement of pieces of machinery and how different systems were to interact. The design was then carried out as the various parts of the facility were built and installed. Software was designed which controlled the different parts of the combustion process and monitored the different products of combustion as well as the properties of the air and fuel used in the combustion. These …

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Optimization Of A Low Heat Load Turbine Nozzle Guide Vane, Jamie J. Johnson Mar 2006

Optimization Of A Low Heat Load Turbine Nozzle Guide Vane, Jamie J. Johnson

Theses and Dissertations

Often turbomachinery airfoils are designed with aerodynamic performance foremost in mind rather than component durability. However, future aircraft systems require ever increasing levels of gas-turbine inlet temperature causing the durability and reliability of turbine components to be an ever more important design concern. As a result, the need to provide improved heat transfer prediction and optimization methods presents itself. Here, an effort to design an airfoil with minimized heat load is reported. First, a Reynolds-Averaged Navier-Stokes (RANS) flow solver was validated over different flow regimes as well as varying boundary conditions against extensive data available in literature published by the …

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Alleviation Of Buffet-Induced Vibration Using Piezoelectric Actuators, Shawn D. Morganstern Mar 2006

Alleviation Of Buffet-Induced Vibration Using Piezoelectric Actuators, Shawn D. Morganstern

Theses and Dissertations

Buffet-induced vibration has been problematic for aircraft structures for many years. The F-16 ventral fin, while prone to these effects, lends itself well to the evaluation of modern active structural and flow control technologies. The objective of this research was to determine the most critical natural modes of vibration for the F-16 ventral fin and design piezoelectric actuators capable of reducing buffet-induced ventral fin vibration. A finite element model (FEM) for the fin was developed, tuned and optimized to closely match published modal frequencies. Piezoelectric actuator patches were designed using the strain characteristics of the FEM and integrated into the …

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Cool Flames At Terrestrial, Partial, And Near-Zero Gravity, Michael R. Foster, Howard Pearlman Jan 2006

Cool Flames At Terrestrial, Partial, And Near-Zero Gravity, Michael R. Foster, Howard Pearlman

Faculty Publications - Biomedical, Mechanical, and Civil Engineering

Natural convection plays an important role in all terrestrial, Lunar, and Martian-based, unstirred, static reactor cool flame and low-temperature autoignitions, since the Rayleigh number (Ra) associated with the self-heating of the reaction exceeds the critical Ra (approximately 600) for onset of convection. At near-zero gravity, Ra < 600 can be achieved and the effects of convection suppressed. To systematically vary the Ra without varying the mixture stoichiometry, reactor pressure, or vessel size, cool flames are studied experimentally in a closed, unstirred, static reactor subject to different gravitational accelerations (terrestrial, 1g; Martian, 0.38g; Lunar, 0.16g; a n dr e - duced gravity, ∼10−2g). Representative results show the evolution of the visible light emission using an equimolar n-butane:oxygen premixture at temperatures ranging from 320 to 350 ◦C (593–623 K) at subatmospheric pressures. For representative reduced-gravity, spherically propagating cool flames, the flame radius based on the peak light intensity is plotted as a function of time and the flame radius (and speed) is calculated from a polynomial fit to data. A skeletal chemical kinetic Gray-Yang model developed previously for a one-dimensional, reactive– diffusive system by Fairlie and co-workers is extended to a two-dimensional axisymmetric, spherical geometry. The coupled species, energy, and momentum equations are solved numerically and the spatio-temporal variations in the temperature profiles are presented. A qualitative comparison is made with the experimental results.

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Neural Network-Based Output Feedback Controller For Lean Operation Of Spark Ignition Engines, Brian C. Kaul, Jagannathan Sarangapani, J. A. Drallmeier, Jonathan B. Vance, Pingan He Jan 2006

Neural Network-Based Output Feedback Controller For Lean Operation Of Spark Ignition Engines, Brian C. Kaul, Jagannathan Sarangapani, J. A. Drallmeier, Jonathan B. Vance, Pingan He

Electrical and Computer Engineering Faculty Research & Creative Works

Spark ignition (SI) engines running at very lean conditions demonstrate significant nonlinear behavior by exhibiting cycle-to-cycle dispersion of heat release even though such operation can significantly reduce NOx emissions and improve fuel efficiency by as much as 5-10%. A suite of neural network (NN) controller without and with reinforcement learning employing output feedback has shown ability to reduce the nonlinear cyclic dispersion observed under lean operating conditions. The neural network controllers consists of three NN: a) A NN observer to estimate the states of the engine such as total fuel and air; b) a second NN for generating virtual input; …

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